The present invention relates to polyurethane reactive adhesive compounds containing finely dispersed polymers and to a process for bonding substrates using such adhesive compounds.
The capacity of inactivated polyisocyanates when mixed with suitable hydroxy functional or aminofunctional compounds, to form mixtures which will remain stable in storage at room temperature for more than six months in the disperse phase has been described in Houben-Weyl, "Methoden der organischen Chemie", Volume 20/2, Thieme-Verlag, Stuttgart 1987. The polyisocyanates may be mixed with suitably selected special hydroxy functional and/or aminofunctional reactants to form mixtures which are stable in storage at room temperature and which can be cured as described in German Auslegeschrift 3,403,499 to form adhesives with very high bond strength. These heat-curable one-component polyurethane adhesive systems which have been prepared from inactivated polyisocyanates and hydroxy-functional and/or amino-functional compounds are stable in storage at room temperature often contain, in their preferred formulations, expensive components which are difficult to synthesize.
Moreover, when these mixtures are used for bonding vertical joints or for forming "overhead bonds" necessitated by the conditions of assembly, the relatively low viscosity of the mixtures may impair the continuity of the adhesive joints.
It was therefore an object of the present invention to provide improved systems based on polyurethane reactive adhesive compounds containing inactivated polyisocyanates.